The invention relates to an optical system, and more particularly, relates to a track traverse signal detecting circuit of an optical disc player, which allows detection of an accurate track traverse signal by adjusting a level of a reference value for shaping a radio frequency (RF) envelope signal based on a Compact Disc or a Digital Video Disc.
Generally, in an optical system, a pickup emits laser light to a disc, receives light reflected from the disc, and then reads data recorded on the disc. At this time, the pickup converts the reflected light into a radio frequency signal and outputs the converted radio frequency signal. The radio frequency signal output from the pickup is then processed by an appropriate signal processor. As a result, a tracking error signal, etc. is generated.
In a conventional optical system, when a pickup jumps tracks or randomly accesses desired tracks, the pickup spot traverses the tracks. A microcomputer calculates the number of tracks to be traversed and controls the pickup to move to the desired tracks.
FIG. 4 is a block diagram of a traverse servo in the optical disc system in prior art. When a pickup 42 jumps tracks or randomly accesses a desired track, the pickup 42 traverses certain tracks of the disc 41. A number of tracks to be traversed is calculated in a microcomputer 46. The pickup 42 also reads data recorded on a disc 41 and outputs a radio frequency (RF) signal. The RF signal is fed to a RF amplifier 43 and a tracking error (TE) generating circuit 45. The amplified RF signal output from the RF amplifier 43 and the TE signal output from the TE signal generating circuit 45 are fed to a track traverse detecting circuit 44. The track traverse detecting circuit 44 outputs a track traverse signal Cout. The microcomputer 46 receives the track traverse signal Cout and calculates the number of tracks to be traversed. The microcomputer 46 commands to a tracking controller 47 to control an actuator driver 48 in a track jump mode or a random access mode and then the actuator driver 48 drives the pickup 42 to jump the calculated tracks so as to move to the desired track. The number of tracks to be traversed is calculated from pulses of the track traverse signal Cout generated in the track traverse detecting circuit 44. Then the microcomputer 46 commands the tracking controller 47 to stoop the pickup 42 on the desired track.
The radio frequency (RF) signal amplified by a RF amplifier 43 and tracking error (TE) signal generated by the TE signal generating circuit 45 are used in generating the track traverse signal Cout in the jump mode. The TE signal and the RF signal may be used as the track traverse signal Cout. However, both signals are used in generating the track traverse signal compensating each other because the track traverse signal Cout is generated every time the pickup 42""s light spot traverses one track.
FIG. 5 is a block diagram of a conventional RF signal processing circuit in the track traverse signal detecting circuit 44. An envelope detector 51 detects a RF envelope signal from the received RF signal. The RF envelope signal is fed to a wave shaping circuit 52. The wave shaping circuit 52 compares the RF envelope signal with a predetermined constant reference voltage and outputs a shaped RF envelope signal. The shaped RF envelope signal is used for a first track traverse signal since its pulse is generated corresponding to the traversed track. To obtain a precise track traverse signal, the TE signal is used as a second track traverse signal at the same time.
However, when the conventional optical system is used for an optical disc player for playing both compact discs (CDs) or digital video discs DVDs, since the (DVDs) have a narrower pitch than the CDs, the amplitude of the RF envelope signal of the DVDs is smaller than that of the RF envelope signal of the CDs.
The different amplitude of the RF envelope signals of CDs and DVDs cause problems with the conventional optical system where the level of a reference voltage Vref 30 for generating the first track traverse signal is fixed to a predetermined reference level according to the pitch of the CDs. Thus, the first track traverse signal is not accurately generated if DVDs are used. This means that the microcomputer 46 is incapable of accurately counting the number of the track to be traversed at all times. Therefore, to correct the unreliability of conventional optical systems, a reference voltage Vref capable of being adjusted according to the use of CDs or DVDs is needed.
To solve the above and other problems with conventional optical systems, an object of the present invention is to provide a track traverse signal detecting circuit which performs track access operation by adjusting the level of the reference voltage Vref according to the CDs or DVDs and generating the exact track traverse signal.
To achieve the above and other objects, one aspect of the present invention is to provide a track traverse signal detecting circuit which comprises a pickup for reading data recorded on a disc and outputting a radio frequency signal; a radio frequency signal processing means for receiving the radio frequency signal from the pickup and amplifying the radio frequency signal and detecting a RF envelope signal from the amplified radio frequency signal; a tracking error signal generating means for generating a track error signal; a first track traverse signal generating means for generating a first track traverse signal based on the tracking error signal; a control means for monitoring the second track traverse signal using the first track traverse signal and outputting a signal for a reference voltage level; a reference voltage generating means for generating the reference voltage Vref based on the reference voltage level signal; and a second track traverse signal generating means for generating a second track traverse signal based on RF envelope signal and the reference voltage Vref
The first track traverse signal generating means according to the present invention may comprise an amplifier for amplifying the tracking error signal output from the tracking error signal generating means; and a comparing means for comparing the tracking error signal with a ground voltage and outputting a high level voltage when the tracking error signal is larger than the ground voltage and a low level voltage when the tracking error signal is smaller than or equal to the ground voltage.
The second track traverse signal generating means according to the present invention may include a comparing means for comparing the RF envelope signal with the reference voltage Vref and outputting a high level voltage when the RF envelope signal is larger than the reference voltage Vref and a low level voltage when said RF envelope signal is smaller than or equal to the reference voltage Vref.
The control means according to the present invention may adjust the second track traverse signal""s frequency to be equal to the first track traverse signal""s frequency.
The control means may further adjust the phase of the track traverse signal based on the first track traverse signal to ensure a 90 degree shift between the phase of the second track traverse signal and that of the first track traverse signal.
In addition, the control means calculates a mean value of the second track traverse signal and outputs a control signal to the reference voltage generating means so as to generate a reference voltage Vref based on the mean value.
Another aspect of the present invention is to provide a track traverse signal detecting circuit which comprises a pickup for reading data recorded on a disc and outputting a radio frequency signal; a radio frequency signal processing means for receiving the radio frequency signal from the pickup and amplifying the radio frequency signal and detecting a RF envelope signal from the amplified radio frequency signal; a control means for determining whether the disc is a Compact Disc or a Digital Video Disc and outputting a signal of a reference voltage level; a reference voltage generating means for generating a reference voltage Vref based on the signal of the reference voltage level; and a comparing means for comparing the RF envelope signal with the reference voltage and outputting a track traverse signal.
Other and further objects, features and advantages of the invention will appear more fully from the following description.